This means a couple things:
1. if you send a TEST frame, you can get multiple responses.
This is manageable, though unwieldy. I doubt the service
providers
want to get a response from the subscriber's printer, for
example.
2. if there is nothing connected to the bridge, you will get no
response.
This would be bad. There is no way to distinguish between a
failed link
and an unutilized link.

OR it would be turned around by the bridge. Bridges have MAC addresses.
In particular, if there is a management entity in a bridge (e.g. the one
you need for OA&M) then it would be a reasonable TEST target

We could define TEST as an
ethertype

It's been done, 9000h

and hope that all the bridge vendors
implement MAC Clients to handle it... but I doubt this would
happen.

Denton Gentry
Dominet Systems

PS: I just noticed an earlier response from Tony Jeffree also
mentioning
bridges, but I'm gonna send this one anyway.